This invention relates to panic exit devices having one or more latches carried by the door which engage receiving portions mounted on door frameworks surrounding the door. In particular, the invention relates to panic exit devices having one or more vertically operating latches at the top and/or bottom of the door. Examples of such devices wherein the bolts may be retracted by a panic exit device are described in U.S. Pat. No. 3,993,335 to Schmidt, U.S. Pat. No. 3,940,886 to Ellingson, Jr., and U.S. Pat. No. 4,839,988 to Betts et.al.
There are numerous types and styles of mechanisms used for operating the popular commercial and industrial door latches wherein the latches such as bolts extend vertically from the top and bottom of the door and engage the top and bottom door frame members. These devices can include a panic bar release mechanism on one side of the door for rapid release of the bolts by depressing the panic bar to open the door.
Another desirable feature of a latch system is a provision wherein after the latch is disengaged by actuating the panic exit device, the latch is retained in a condition for easy re-engagement when the door closes. In an extending bolt-type latch a mechanism for retaining the retracted bolt in a retracted position after the door is opened and continuously while the door is opened, can serve this function. This feature prevents the need to continue pressure on the panic bar or the key in order to prevent the bolt from interfering with objects such as the ground or the door frame while the door is being opened and returned to the closed position. Thus, the bolt retaining mechanism is designed to hold the bolt in a retained condition and to trigger and release the bolt when the door again reaches the closed position. U.S. Pat. Nos. 4,283,882, 3,993,335 and U.S. Pat. No. 3,334,500 show such bolt or latch mechanisms.